Engine cylinder



Aug. 23, 1938. o. MADER ENGINE CYLINDER Filed April 15, 1955 2 Sheets-Sheet 1 In venfpn' 3, 1938. o. MADER 2,127,825

.ENG'INE CYLINDER Filed April 15,. 1935 2 Sheets-Sheet 2 III,

' Patented Aug. 23, 1938 UNITED, STATES ENGINE CYLINDER Otto Mailer, Dessau-Ziebigk, Germany, aasignor to Junkers Flugzeug-und-Motorenwcrke Ak-a tiengcsellschait, Dessau, Germany Application April 15, 1935, Serial No. 18,415

a In Germany April 23,193

'1 Claims.

My invention relates to internal combustion engines and more especially to the construction tion chamber, or by an increase of the number of revolutions. Both means act towards increasing the heat flow in the engine and the control of this increased heat flow is therefore decisive for the possibility of obtaining an increase of performance. This is particularly true of the cylinder wall, on which the piston slides, since this wall is relied upon to abduct towards the outside not only the heat directly transierred. onto it by the combustion gases, but also a considerable part of the heat taken up by the piston and since in spite of this heavy load of heat abim duction this wall must form a reliable sliding surface for the piston. a

Hitherto great difliculties were encountered whenever it was tried to increase the performance of liquid-cooled engines, the cylinders oi" which m were equipped with liners, for the flanges or threaded parts which'serve to connect the end adjoining the combustion chamber of such liner to the other parts (water jacket, cover etc.)

of the cylinder in a gasand liquid -tight manher, form local accumulations of material which present longer paths for the abduction of heat,

and thus form the cause of accumulations of heat and irregular distribution of temperature, which are likely to cause a distortion of the liner and jamming of the piston. This is true more particularly in the case, where the gas pressures acting in axial direction are taken up and transmitted by the liner, since in such a case the liner,

in order-to be strong enough, must be formed with, a thicker wall than if it is not required to transmit axial forces.

I obviate these difllculties by forming the liners of internal combustion engines, in which the liners are separated from the cylinder block or cooling jacket and are water-cooled and do not participate in the transmission of the gas pressures in axial direction, throughout the area of the highest combustion pressures and temperatures with walls, the thickness of which merely 66 sufilces to reliably takeup the gas pressures acting in a direction transversely toithe cylinder axis, without presenting any local accumulation of material. In this zone of highest pressures and temperatures the new liners thus form simple thinwall tubular rotation bodies and they are further 6 mounted in the cooling jackets in such manner that at least this zone oi highest heat stresses is outwardly in contact with cooling water practi-. cally everywhere. Preferably the points, at which the members (such as screw bolts or the like) W hold the liner in place in the cylinder and connected with the liners, are located outside of this zone. 1

Of all forces acting on it from without, the liner is merely required to ,take up the pressure m necessary to tightly fit the liner to the cylinder body and the sliding pressure of the piston directed transversely to the axis. These forces are however small as compared to. the gas pressure forces acting in the radial direction, so that they 20 need scarcely be considered in selecting the wall thickness of the liner.

Preferably the liner is allowed some play in radial direction relative to the cylinder body in order to enable these two parts to shift somewhat in radial direction relative to each other.

As compared with the design of cylinders hith-- erto used in connection with internal combustion engines, the new cylinder construction according to, the present invention involves quite a number of important advantages, more especially as regards the possibility of increasing the performance of the engine.

The possibility of forming the liner in the area of the highest heat stresses with a thickness of 35 wall, which is solely determined by the gas pressure acting in radial directionand which may therefore be very low, enables the paths of heat to become very short and the diiferences'of temperature arising in the liner body to remain como paratively small. A liner of this kind having a particularly thin wall ree from local accumulations oi material presents a certain flexibility in radial directlon,,which isimportant in several respects. Owing to this flexibility for instance local accumulations of stresses in the liner, such as are brought about by the transverse forces created by the piston or by nou -uniform changes of form of the cylinder head, will arise, if at all, only to a' small extent. Furthermore this flexibillty favors considerably the tight fit between the liner and the piston, since the thin liner is'also capable of adapting itself to a certain extent to the far more rigid piston. Hitherto merely the packing members associated with the piston (the piston rings) were capable of such an adaptation, while in contradistinction thereto the piston and -liner had to be considered as relatively rigid bodies which were therefore required to cooperate with so much play, that also-in the case of irregular changes of form of the liner no jamming of the piston would occur.

In view of the very low width of the surface of contact between the liner and the cylinder head the cylinders can be arranged in very close juxtaposition without the cooling liquid being thereby prevented from passing through between two adjoining cylinders. This arrangement involves a very small overall length in the direction of the crank shaft and correspondingly low weight of the engine without involving irregularities of cooling and wearing out-of-true of the liner.

The new cylinder-construction is therefore particularly suitable for use in connection with socalled cylinder blocks in which a plurality of liners is accommodated within a common water jacket, the particular advantage oflered by such an arrangement consisting in that each individual liner is free to expand independently of the other liners and of the water jackets, so that the difflculties which frequently arise in cylinder blocks provided with individual liners are avoided.

In engines formed with a cylinder head separated from and disengageably connected with the water jacket (this cylinder head extending either over one or a plurality of cylinders) it is advantageous to, press the liner or liners directly against the cylinder head, since in this case an unfavorable accumulation of material at the walls of the combustion chamber, which are exposed to the highest temperatures, can be easily avoided and a far more uniform cooling of these walls attained, and since the packing of the parts hecomes far more simple and reliable by being subdivided into two separate and independent packings (one between the inner wall of the cylinder head and the liner and another one between the outer wall of the cylinder head and the water jacket) than the usual flange packing between the cylinder block and the cylinder head, which is relied upon to simultaneously pack the combustion chamber relative to the cooling chambers and the ambient air.

The new liners render the engine particularly suitable for hot cooling, 1. e. for cooling with liquids of higher boiling point than water, since in spite of a higher temperature of the cooling agent, no local superheating and consequent warping of the liner need be feared.

The liner is pressed against its seat on the cylinder head by means of elastically yielding members in such manner that at all heat conditlons of the engine a sunlcient packing pressure is provided. The liner may for instance be pressed onto its seat by axially acting springs inserted between the liner and the cooling jacket. The liner may howeveralso be held down on its seat by screw bolts which extend from a point on the liner remote from the seat to a point of the cylinder head. The screw bolts thus become comparatively long and since they are only required to exert a low packing pressure, they may be very thin and consequently very elastic. I have found it particularly useful to employ screw bolts extending across the cooling space since in this case these bolts assume substantially the same temperature as the adjoining parts ofthe cylinder and, on the temperature of the cooling agent changing, will expand and contract similarly as the cylinder, so that the tightening pressure is practically not influenced by the varying thermic condition of the engine.

In the drawings aflixed to this specification and forming part thereof several embodiments of my invention are illustrated diagrammatically by way of example.

In the drawings Fig. 1 is an axial section on the line II of Fig. 2, and

Fig. 2 is a cross section on the line II-II of Fig. 1, of part of a cylinder block of an internal combustion engine embodying my invention.

Fig. 3 is an axial section illustrating another modification.

Fig. 4is an axial section on line IVIV oi. Fig. 5 and 1 Fig. 5 is a cross section on the line V-V in Fig. 4, of the cylinder of a twin piston engine embodying my invention.

Referring first to Figs. 1 and 2, i is the water jacket of a block of cylinders, 2 is the-cylinder head, which covers a plurality of cylinders and is formed with cavities 3 for the passage of cooling liquid. 4 are the liners, each of which-extends over the entire path of the piston. The

inner wall 5 of the cylinder head does not come in contact with the piston and the material, of which the cylinder head is made, may therefore be selected without paying regard to sliding resistance. The part of the liner adjoining the combustion chamber, 1. e. the area of highest pressures and temperatures, is formed as simply and uniformly as possible, presenting no projecting flanges nor other local accumulations of material. The wall thickness of this part of the liner is determined substantially only by the consideration that the liner must be capable of taking up the gas pressures acting in radial direction. Consequently, more especially if the liner is made of steel, only a comparatively low wall thickness is required. I have found that this low wall thickness also suiilces for effecting a tight fit at 6 between the cylinder head and the liner so that I am enabled to avoid the usual broad flanges which create a considerable accumulation of heat and easily lead to warping, i. e. to a wearing outof-true of the liner and to jamming of the piston. I may pack the joint between the end face .01 the liner and its seat in the cylinder head by means of a ring 6 of elastic material (copper or the like). The cooling chamber 1 surrounding the liner 4 may be packed relative to the crank case in the usual manner, for instance by means of a rubber packing I embedded between annular flanges 0 formed on the liner and resting against an annular surface ill formed on the inner wall of the cooling jacket. The liner 4 is pressed onto its seat in the cylinder head by means of long thin rods with threaded ends forming screw bolts i2, one end of which is fixed in projections is formed on the liner remote from the seat 8, while their other ends are fixed in the outer wall of the cover 2. The bolts I! extend through the cooling chambers I and I of the jacket and cover and are ther'efore subjected to the same influences of temperature as the other parts of the cylinder. All heat expansions of these parts therefore occur always in the same sense and I thereby obtain a particularly reliable tight fit at 6, since the long thin screw bolts possess a comparatively considerable longitudinal elasticity resulting in a yielding pressure and since variations of temperature cannot materially influence their elasticity.

The circumstance that the projections 13, to which the bolts I2 are fixed, are arranged at a comparatively great distance from the-seat i of the liner, renders it possible to form the wall of the liner in the proximity of the seat in an altogether uniform manner tree from any variations in thickness which might lead to accumulations of heat and might impair the flexibility of the liner.

The liner is evenly cooled over the entire length of the .cooling jacket, also at the point between two adjoining liners. This is particularly important since the heat transferred in the combustion chamber to the liner is enabled to flow towards the outside here also on the shortest radial path, while in the cylinders hitherto used the path to be traversed by the heat in circumferential direction before reaching the cooling water, was longer, resulting in accumulations of heat, warping of the liner and other difllculties.

In the modification illustrated in Fig. 3, the liner 4 is resiliently pressed against its seat in the cylinder head by a coil spring i5 inserted between an annular flange IS in the jacket and the annular flange 9 of the liner adjoining the rubber packing 8.

Fig. 4 illustrates a cylinder of a twin piston enginein which 2| is the cooling jacket formed with an inwardly projecting flange 22, the cylindrical .surface of which also forms part of the combustion chamber. situated in the middle part of the cylinder. 23, 24 are two liners designed to guide the two oppositely reciprocating pistons (not shown). The adjoining end faces of these liners are forced against their seats in the flange 22 by means of long thin screw bolts 25, the heads 26 of which rest against a flange 21 near the outer end of liner 23, while the nuts 28 abut against the flange 29 near the outer end of liner 24. 40 and 4| are the ,cylinder and the jacket MCovers, respectively, and 42 are screw bolts fixing these parts on the liners and jacket, respectively. Here also the parts of the liners which are. influenced by the high pressures and temperatures are thin and free from any accumulations of material. Only in the middle portion of the liners, near and to the rear end of the scavenging and exhaust ports 3! and 32, the liners are formed with flanges 33, 34, which are traversed radially by the scavenging and exhaust ports and axially by the cooling water chanels 35, 38, through which extend also the screw bolts 25. The great length of these bolts, which extend through the cooling medium, causes the liners to be'pressed 55 against their seats in an elastic manner, which is not influenced by changes in the operative condition of the liners.

I wish it to be understood that I do not desire to be limited to the exact details of construction shown and-described for obvious modifications will occur to a person 'skilledin the art.

I claim:-

1. In a liquid cooled internal combustion engine in combination, a cooling jacket, a cylinder cover associated with said jacket, a separate cylinder barrel or liner mounted in said jacket and a piston movable in said liner, said liner having the form of a thin-walled tube throughout that part which extends over the area of the higher temperatures and pressures, a seat on said cover for the end of said liner adjoining the combustion chamber, elastic means arranged to act on a point of said liner outside of said area, for pressing said end of the liner onto said seat, and means for relieving said liner from the gas pressures acting on said cover and piston.

2. The engine of claim 1 in which means are provided on the part of the liner outside of the area of the higher temperatures and pressures for centering and packing said liner in said jacket.

3. The engine of claim 1, in which the liner is mounted in the jacket with a. clearance and the means for pressing the end of the liner onto its seat extend in this clearance.

4. The engine of claim 1 in which the means for pressing the liner onto its seat is a spring.

5. The engineof claim 1 inwhich the means for pressing the liner onto its seat are rods forming screw bolts which extend through the cylinder cover.

6. In a liquid cooled internal combustion engine in combination, a cooling jacket, two separate liners mounted in said jacket in axial alignment, said liners having the form or thin-walled tubes throughout that part which extends over the area of the higher temperatures and pressures, an annular flange projecting inwardly from said jacket between the adjoining ends of said liners, seats for the said liner ends formed on said flange, elastic means arranged to act on points of said liners outside of said area, for pressing said liner ends onto said seats and means for re lieving said liners from the gas pressures actin on said pistons.

7. The engine of claim 6, in which the elastic pressing means are formed as long thin screw bolts extending throughout the length of said jacket and between said jacket and said liners. OTIO MADER. 

